Computer systems are designed to be able to continuously operate under varying degrees of thermal loading. As the operating power consumption of computer systems creeps upwards, the thermal budgets of these systems have become tighter. It is now a challenge to design a computer system to operate continuously under worst-case thermal loading for extended periods of time, while at the same time both maintaining a desired range of operating performance and maintaining the temperature of the computer housing within safety limits.
Further, computer systems are being packed into smaller profile housing to improve portability. As a result, many electronic devices have “hotspots” where there is a potential to overheat and cause injury to the person using the electronic device. These hotspots are the result of computer systems such as laptop computers having both compact housing (also called skin) and limited cooling capacity. The UL and other government bodies establish safety standards for products. As a result, manufacturers of computer systems and other electronic products are required to limit the skin temperature to levels within government approved safety limits so that they are free from reasonably foreseeable risks of fire, burn and other related hazards.
To resolve thermal issues, several proactive measures have been developed including thermal-throttling, engaging cooling fans, providing heat exhaust pipes, managing and redistributing power, switching from external graphics to internal graphics, and etcetera. Many systems designed today require these proactive measures to provide adequate performance under various thermal conditions. Temperature sensors may be used to determine the ambient temperature of the working environment of computer systems. Thermal models may then be developed based on data collected from these temperature sensors.
However, temperature sensors are often implemented as integrated circuits which can only be placed at a limited number of locations around the computer system and its skin. Also, thermal sensors can be integrated circuits, so using a large number of thermal sensors may in some cases be cost-prohibitive. FIG. 1 illustrates an example of a location to measure ambient temperature for thermal control. In the illustrated embodiment, temperature sensor 101 is positioned in the middle portion of the display panel of a portable computer 100. Temperature sensors may be placed in various places within a computer system such as, for example, on the microprocessor (CPU) die, in the proximity of the CPU die (CPU Prox), on known hotspots such as a motherboard, on a hard drive device, on a heat pipe, on a battery, on a track pad, and etcetera.
Often, a hotspot may be located on a particular point where it is difficult to put a sensor such as the bottom case of a laptop computer system. These points may be generally referred to as critical points. Thermal models may be generated to accurately estimate the temperature at these critical points based on data received from temperature sensors to estimate the temperature at the critical point. These thermal models may be generated so that proactive measures may be taken to mitigate the thermal behavior at hotspots such as turning on the system fans and so on.